The present invention is directed to a treatment for injured or degenerated intervertebral discs. Specifically, the present invention is a method and apparatus for strengthening an injured or degenerated intervertebral disc and relieving pain. The treatment may allow a spine surgeon to avoid a discectomy and removal of the nucleus pulposus during laminectomy operations and may reduce postoperative discogenic pain.
As shown in FIG. 1, each intervertebral disc 10 is a cushionlike pad with top and bottom endplates adjoining the bone surfaces on each adjacent vertebral body 20. As shown in FIG. 2, each disc has an inner sphere, the nucleus pulposus 30, which acts as a cushion for compressive stress. Around the nucleus pulposus is an outer collar of approximately 12 concentric rings, the annulus fibrosis 40, which limits the expansion of the nucleus pulposus when the spine is compressed. The rings of the annulus fibrosis also bind the successive vertebrae together, resist torsion of the spine, and assist the nucleus pulposus in absorbing compressive forces.
The grains of collagen fibers in adjacent rings of the annulus fibrosis 40 run in different directions so that the grains cross like an X. This arrangement of the collagen layers allows the spine to withstand twisting, shear forces.
FIG. 2 shows an exemplary injury to an intervertebral disc. A herniated or prolapsed disc is commonly called a xe2x80x9cslipped disc.xe2x80x9d Severe or sudden trauma to the spine or nontraumatic pathology such as degenerative spine disease may cause a bulge, rupture, degeneration, or other area of injury (xe2x80x9cinjuryxe2x80x9d) 50 in one or more intervertebral discs. The annulus fibrosis 40 is thinnest posteriorly in the general direction of the spinous process 60, so the nucleus pulposus 30 usually herniates in that direction. The injury usually proceeds posterolaterally instead of directly posteriorly because the posterior longitudinal ligament strengthens the annulus fibrosis at the posterior sagittal midline of the annulus. The terms xe2x80x9cposteriorxe2x80x9d and xe2x80x9cposteriorlyxe2x80x9d mean the general posterior and posterolateral aspects of the disc as distinguished from the anterior aspects of the disc. The posterior aspect of the annulus fibrosis is also the location of vulnerable nerve tissues, including but not limited to the cauda equina 70 and spinal nerve roots 80.
A posterior injury of the nucleus pulposus often impinges on the spinal nerve roots 80 exiting the spinal canal 90. The resulting pressure on these nerve roots often leads to pain and/or numbness in the lower extremities. Injured intervertebral discs are treated with bed rest, physical therapy, modified activities, and painkillers over time. If these treatments are ineffective, the injured and usually protruding disc is often surgically removed.
Current treatments offer only limited success in avoiding surgical removal of injured intervertebral discs that do not heal themselves over time. A few treatments are adopted for use on an intervertebral disc from broad methods to shrink collagen in various other parts of the body. Several treatments attempt to reduce discogenic pain.
Several exemplary prior art references disclose using heat to shrink collagen. U.S. Pat. Nos. 5,374,265 and 5,484,432 to Sand (the xe2x80x9cSand referencesxe2x80x9d) are directed to methods for shrinking collagen with an infrared laser. The collagen shrinkage in the Sand references is generally accomplished in an ophthalmological context. Laser light that is optimally absorbed by collagen tissue is applied to a corneal stoma resulting in collagen shrinkage and reshaping of the cornea for vision correction. Although the Sand method generally applies to shrinkage of collagen, it only contemplates applying relatively small amounts of energy to delicate eye tissue. No provision is made for protecting vulnerable tissue near collagen in other parts of the body. The amount of energy needed to shrink collagen in synovial joints or the spine is greater than the amount needed for eye tissue and may damage vulnerable tissue near the collagen being treated.
U.S. Pat. Nos. 5,458,596 and 5,569,242 to Lax et al. (the xe2x80x9cLax referencesxe2x80x9d) are directed to broad methods and apparatuses for controlled contraction of soft tissue. The Lax references disclose the application of radio frequency energy through an electrode to tissue containing collagen. Such an application of energy as envisioned by the Lax references to an intervertebral disc would damage vulnerable tissues near the application site. The Lax references do not disclose the use of energy other than radio frequency. The shape of the Lax electrode is not designed for use on the spine. Also, because the Lax electrode is a general applicator, it does not protect vulnerable tissues during application of energy and therefore would not be suitable for applications involving the spine.
U.S. Pat. No. 5,954,716 to Sharkey et al. (the xe2x80x9cSharkey ""716 referencexe2x80x9d) is directed to a method and device for modifying the length of a ligament. In the Sharkey ""716 reference, radio frequency energy is applied to one ligament in a set of opposing ligaments. Only radio frequency energy is disclosed. The radio frequency energy shrinks one ligament, restoring equal length and a balance of function to the set of opposing ligaments. Although the Sharkey ""716 treatment uses radio frequency energy to shrink a ligament, it would not work on an intervertebral disc because an intervertebral disc is surrounded by vulnerable tissues. Because intervertebral discs lie close to the spinal canal and spinal nerve roots, application without thermal protection of radio frequency energy suitable for shrinking a ligament might harm vulnerable nerve tissues.
Heating an intervertebral disc for relief of discogenic pain is disclosed in U.S. Pat. Nos. 5,433,739 and 5,571,147 to Sluijter et al. (the xe2x80x9cSluijter referencesxe2x80x9d). In the Sluijter references, probes are inserted into an intervertebral disc by puncturing the annulus fibrosis. Radio frequency or direct current energy is delivered through probes to heat the nucleus pulposus of a disc to approximately 60xc2x0 C. to 70xc2x0 C. The heat travels to the outer perimeter of the disc being treated so that the entire disc is heated. The applied heat relieves back pain by denervating fine nerve endings in the disc. Although the probes of the Sluijter references may relieve back pain, the Sluijter probes invade the disc and are not intended to shrink collagen or repair a bulging, ruptured, or injured intervertebral disc. Since the entire disc is heated to approximately 60xc2x0 C. to 70xc2x0 C., the heat may harm vulnerable tissues near the disc and have other thermally detrimental side effects. Some recent studies have shown that the amount of thermal energy provided to the posterior annulus by the IDET procedure is insufficient to cause either shrinkage/strengthening of the posterior annulus or ablation of the pain-sensing posterior annular nerve endings.
Several prior art references disclose methods for applying energy to the interior of an intervertebral disc by invading the disc with a needle or catheter. For example, U.S. Pat. No. 5,865,833 to Daikuzono is directed to a device for laser treatment. The Daikuzono device is for a discectomy procedure and for removal of intervertebral disc tissue, not to avoid a discectomy or to preserve disc tissue or ablate posterior annulus pain-sensing nerve endings. The Daikuzono method uses a hollow needle that is advanced into the center of an intervertebral disc, and then disc tissue is vaporized with laser energy and the vapor removed through the hollow needle. The hollow needle invasively punctures the disc.
U.S. Pat. Nos. 6,007,570, 6,073,051, 6,095,149, and 6,122,549 to Sharkey et al. (the xe2x80x9cSharkey referencesxe2x80x9d) are directed to methods for treating an intervertebral disc and to devices with tip portions for performing various functions on a disc. Externally guidable catheters having one lumen or several lumina puncture the annulus fibrosis of an intervertebral disc and are inserted into the nucleus pulposus at the center of the disc. Functional tips on the distal ends of the catheters add or remove material or deliver energy. The Sharkey references also disclose injecting a sealant into fissures in the annulus fibrosis. The methods and devices of the Sharkey references have the advantage of treating an intervertebral disc from the inside, thereby using the annulus fibrosis of a disc as thermal insulation from the spinal canal. The Sharkey methods and devices, however, have the disadvantage of not being able to reach many types of bulges, ruptures, or areas of injury in or near the outer layers of the annulus fibrosis. Further, because they puncture the disc, the Sharkey catheters are invasive and larger puncture holes are needed in order to use larger functional tips. The Sharkey methods and devices do not provide a noninvasive external approach to disc repair, and require maneuvering a catheter inside an intervertebral disc. They also do not ablate nerve endings in the posterior annulus and do not shrink/strengthen the posterior annulus.
Known prior art methods for treating an injured intervertebral disc are invasive to the disc, do not shrink/strengthen the posterior annulus, do not ablate the pain-sensing nerve endings in the posterior annulus, and may be thermally unsafe to vulnerable tissues around the spine.
The present invention provides a method and apparatus for shrinking and strengthening the cartilaginous or collagenous material (xe2x80x9ccollagenxe2x80x9d) near an injury in the annulus fibrosis or the nucleus pulposus of one or more intervertebral discs. The present invention may allow a spine surgeon to avoid a discectomy and removal of the nucleus pulposus during a laminectomy operation.
The present invention""s epidural and extradiscal approach to repairing a disc prevents the invasion of a disc with a needle or catheter. Needle and catheter methods puncture the intervertebral disc being treated, thereby exacerbating the very condition sought to be cured or may introduce infection into the nerve space.
The present invention may eliminate or greatly reduce discogenic pain by thermally destroying nerve endings that transmit pain sensation from the posterior annulus. The surface area of the posterior annulus that can be treated for the reduction of discogenic pain is not limited as in prior art methods that deliver energy from a device inside the disc.
During thermal treatment by the present invention, vulnerable tissues near a disc undergoing treatment may be thermally insulated or cooled and/or displaced away from the thermal energy and thereby protected from potentially destructive heat. Laser embodiments of the present invention may achieve thermocoagulation of disc tissue by short laser bursts that confine heating to the disc. This thermal confinement combined with posterior displacement of neural structures may protect these vulnerable tissues near a disc without requiring insulation or cooling of the vulnerable tissues.
The present invention""s strengthening of collagen may result in the reduction of future incidents of disc herniation, reduction of spinal nerve-root impingement, and reduction of discogenic pain arising from nerve endings in posterior annulus.
The present invention is directed to an apparatus for thermally treating intervertebral discs using an energy application head having an energy application region and a tissue protecting region. A control member is operationally connected to the energy application head to control the energy application head during treatment of an intervertebral disc.
The present invention also includes a method for thermally treating an injured intervertebral disc while thermally protecting vulnerable tissues. The method includes gaining access to a vertebral column, epidurally approaching the posterior aspect of an injured intervertebral disc, and evaluating the extent of disc injury. The evaluation preferably includes calculating an amount of energy needed to thermally refurbish the intervertebral disc. Energy is applied to the posterior aspect of the injured intervertebral disc while maintaining a safe temperature in vulnerable tissues near the disc. The energy delivered is monitored and the shrinkage and strengthening of the disc may be observed to determine if additional energy is required by the disc or adjacent discs. Further energy may be applied to other posterior areas of the disc to reduce pain. The steps of this method may be performed in alternate order. Steps that are unnecessary in a specific surgery may be omitted.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.